Apparatus for and Method of Controlling a Predistorter, and Method of Detecting Power Control State

1. A method of controlling a predistorter for predistorting a signal input into a power amplifier, the method comprising: storing predistortion coefficients used by the predistorter; acquiring indices each representative of an output power of the power amplifier; detecting, based on the indices acquired in the acquiring, whether the power amplifier is in a state of undergoing power control; and supplying the stored predistortion coefficients to the predistorter when it is detected that the power amplifier is in the state of undergoing power control, or supplying, when it is detected that the power amplifier is not in the state of undergoing power control, to the predistorter predistortion coefficients calculated by a unit that performs predistortion coefficient adaptive updating operation.

2. The method according to claim 1 , wherein the detecting includes: registering a plurality of the indices which are acquired within a predetermined time period; acquiring a difference between a maximum value and a minimum value within the plurality of indices; determining, based on the difference, whether the power amplifier is in the state of undergoing power control; and outputting a signal indicating whether the power amplifier is in the state of undergoing power control.

3. The method according to claim 2 , wherein the predetermined time period is greater than or equal to a converging time of an update algorithm of the unit that performs predistortion coefficient adaptive updating operation.

4. The method according to claim 2 , wherein an output from the predistorter is input into the power amplifier via a variable gain attenuator, wherein the plurality of indices are acquired in the acquiring by sampling an output from the variable gain attenuator.

5. The method according to claim 2 , wherein it is determined in the determining whether the difference is greater than a predetermined threshold; when the difference is greater than the predetermined threshold, it is determined that the power amplifier is in the state of undergoing power control; when the difference is not greater than the predetermined threshold, it is further determined in the determining whether a plurality of the differences acquired in the acquiring within a particular time are not greater than the predetermined threshold; when it is determined that the plurality of differences acquired in the acquiring within the particular time are not greater than the predetermined threshold, it is determined in the determining that the power amplifier is not in the state of undergoing power control.

6. The method according to claim 1 , wherein when it is detected in the detecting that the power amplifier is not in the state of undergoing power control, the supplying delivers the stored predistortion coefficients to the unit that performs predistortion coefficient adaptive updating operation, as an initial value for the unit that performs predistortion coefficient adaptive updating operation to perform the predistortion coefficient adaptive updating operation, and supplies to the predistorter the predistortion coefficient calculated by the unit that performs predistortion coefficient adaptive updating operation.

7. The method according to claim 6 , wherein when it is detected in the detecting that the power amplifier changes from the state of not undergoing power control to the state of undergoing power control, the method further updating the stored predistortion coefficients by using the predistortion coefficient calculated by the unit that performs predistortion coefficient adaptive updating operation at the last timing the power amplifier is not in the state of undergoing power control.

8. The method according to claim 7 , wherein the updating uses the predistortion coefficient calculated at the last timing to update a predistortion coefficient in the stored predistortion coefficients and corresponding to the index acquired in the acquiring at the last timing, and a predistortion coefficient adjacent thereto.

9. A method of detecting power control state for detecting whether a power amplifier is in a state of undergoing power control, the method comprising: registering a plurality of indices which are acquired within a predetermined time period, each representative of an output power of the power amplifier; acquiring a difference between a maximum value and a minimum value within the plurality of indices; determining, based on the difference, whether the power amplifier is in the state of undergoing power control; and outputting a signal indicating whether the power amplifier is in the state of undergoing power control.

10. An apparatus for controlling a predistorter for predistorting a signal input into a power amplifier, the apparatus comprising: a storing unit, for storing a predistortion coefficient used by the predistorter; an index registering unit, for acquiring indices representative of an output power of the power amplifier; a power control state detecting unit, for detecting, based on the indices acquired by the index registering unit, whether the power amplifier is in a state of undergoing power control; and a coefficient supplying unit, for obtaining the stored predistortion coefficient for supplying to the predistorter when the power control state detecting unit detects that the power amplifier is in the state of undergoing power control, and for supplying, when it is detected that the power amplifier is not in the state of undergoing power control, to the predistorter predistortion coefficients calculated by a unit that performs predistortion coefficient adaptive updating operation.